<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .parent{
            width: 500px;
            height: 500px;
            background:paleturquoise;
            position: relative;
        }
        .box{
            width: 200px;
            height: 200px;
            background: red;
            position: absolute;
            /* 子下对父下，子右对父右 */
            bottom: 0;
            right: 0;
        }
    </style>
</head>
<body>
    <div class="parent">
        <div class="box"></div>

    </div>
</body>
</html>